• Suliman (2/2) Jul 24 2017 Why D have two function `contains` and `canFind` if C# have only
• =?UTF-8?Q?Ali_=c3=87ehreli?= (15/17) Jul 24 2017 std.algorithm.canFind and std.range.SortedRange.contains:
• Cym13 (3/9) Jul 24 2017 I'm gessing this predates design by introspection as it would be
• Seb (8/19) Jul 24 2017 Yes - since end of 2016 `find` (and thus `canFind`) do
• Timon Gehr (3/4) Jul 24 2017 `contains` guarantees logarithmic running time, while `canFind` can be

Suliman <evermind live.ru> writes:

contains and it's enough?

=?UTF-8?Q?Ali_=c3=87ehreli?= <acehreli yahoo.com> writes:

On 07/24/2017 11:19 AM, Suliman wrote:

 contains and it's enough?

std.algorithm.canFind and std.range.SortedRange.contains:

   https://dlang.org/phobos/std_algorithm_searching.html#.canFind

   https://dlang.org/phobos/std_range.html#.SortedRange.contains

canFind() is more general because it works with any input range. For 
that reason, it has to walk from the beginning to the end. (O(N) complexity)

contains() requires a sorted random access range so that it can use the 
O(log N) binary search algorithm.

When you have a large sorted array, use contains(). Even if the array is 
not sorted but there are many searches to be performed, sorting first 
and then calling contains() many times may be faster than canFind().

Even if the array is not sorted but it's small, you can use canFind() 
without worrying about performance. Of course it all depends on what 
small and large mean. :)

Ali

Cym13 <cpicard openmailbox.org> writes:

On Monday, 24 July 2017 at 18:31:09 UTC, Ali Çehreli wrote:
 On 07/24/2017 11:19 AM, Suliman wrote:
 [...]

 only
 [...]

 std.algorithm.canFind and std.range.SortedRange.contains:

 [...]

I'm gessing this predates design by introspection as it would be 
cleaner to let the compiler do the switch itself.

Seb <seb wilzba.ch> writes:

On Monday, 24 July 2017 at 19:53:34 UTC, Cym13 wrote:
 On Monday, 24 July 2017 at 18:31:09 UTC, Ali Çehreli wrote:
 On 07/24/2017 11:19 AM, Suliman wrote:
 [...]

 only
 [...]

 std.algorithm.canFind and std.range.SortedRange.contains:

 [...]

 I'm gessing this predates design by introspection as it would 
 be cleaner to let the compiler do the switch itself.


Yes - since end of 2016 `find` (and thus `canFind`) do 
introspection:

https://github.com/dlang/phobos/pull/4907
https://github.com/dlang/phobos/blob/57b8d2511ea37cd01665b9b663d8ba246144b1f9/std/algorithm/searching.d#L1509

Thus, I believe it would be best to deprecate 
SortedRange.contains:

https://github.com/dlang/phobos/pull/5651

Timon Gehr <timon.gehr gmx.ch> writes:

On 24.07.2017 20:19, Suliman wrote:
 Why D have two function `contains` and `canFind`

`contains` guarantees logarithmic running time, while `canFind` can be 
linear.